The present invention relates to a gate valve and to an improved lubricated seal for the seats within the gate valve which surround the passages therein and engage the exterior of the gate.
An example of the type of valve to which the present invention may be applied is the McEvoy Model C Valve. This valve is illustrated on page 864-7 of the Cameron Iron Works, U.S.A., Inc. catalog of 1988 as published in the Composite Catalog by World Oil Publishing Company, Volume 1, page 864-7 of the '88-'89 Edition. This shows and describes a gate valve which includes a pair of seats between the inner ends of the passages and the gate which are each provided with a pressure responsive system for the automatic injection of sealant for a self-sealing action to provide operation long after normal wear on the gates and seats would have caused other valves to leak.
U.S. Pat. No. 4,264,054 discloses a gate valve with an automatic sealant injection system to inject sealant through the seat rings and assist in sealing between the seat ring and the counterbore in the body in which the seat ring is positioned. The patent discloses a particular type of sealing structure including a dished metal ring gasket and a retainer ring. The sealant injection system is exposed to the pressure within the valve chamber for the powering of the sealant injection.
U.S. Pat. No. 4,363,465 discloses another gate valve having automatic sealant injection associated with the seat rings and discloses specific stem sealing means including dished metal ring gaskets.
U.S. Pat. No. 4,541,449 discloses a special seat ring for a gate valve in which the seat ring has a lip biased to seal against the body surface and being exposed to the pressure in the valve chamber to prevent bypass leakage through the valve chamber. Another structure of a seat ring with a lip seal is disclosed in U.S. Pat. No. 4,568,062. Another type of gate valve seat ring having a tubular extension which provides an interference type lip seal in the seat recess in the valve body, is disclosed in U.S. Pat. No. 4,489,918.
U.S. Pat. No. 4,124,194 discloses a gate valve structure in which the seat ring includes a support member, a flexible member and the seat member which is urged by the flexible member positioned between the seat member and the support member into engagement with the gate. The seat member has lip seals for engaging the gate.
U.S. Pat. No. 3,273,855 discloses a variety of seat rings with lip seals and other sealing means for sealing against the seat ring recess in the body and against the gate.